Clinching of superposed sheet materials by means of cooperating punches and dies driven by a press is a wellknown technique. Briefly, a portion of the superposed sheets is displaced orthogonally with respect to a sheet plane by means of a punch penetrating into the sheet material which is supported by a die. The die comprises an anvil, the displaced material is compressed between anvil and punch. Thereby, the displaced material is squeezed and cold-flows laterally thereby forming the clinch connection. In order to permit lateral material flow, the die comprises shaping elements which are stationary during the displacement step but may laterally yield when the cold flux occurs. Elastic means are provided to restore the rest position of the shaping elements.
Restoration of the shaping elements may be performed in that the shaping elements are themselves elastically deformable. An example of this prior art is disclosed in United Kingdom Patent Application 2 069 394. There is a need for a compromise between sufficient strength of the shaping elements to resist forces acting on them during sheet material displacement and sufficient yielding motion for cold-flowing sheet material.
In another prior art design, restoring cushions or rings made of elastomeric material enclose the shaping elements. An example is illustrated in German Patent Application 37 13 083. Such material, however, is easily damaged due to contact with cutting edges and the like, and it may also be susceptible to chemical attack, e.g. of solvents.
Finally, clinching dies are known wherein the shaping members are rugged but are biased into their rest position and positioned by means of leaf springs; such leaf springs are rivetted or screwed on an anvil or a support member of the latter. Examples are disclosed in U.S. Pat. No. 4,972,565 or European Patent 523 473. A drawback is the complicated and time-consuming assemble of the die and, most importantly, that the die may be manipulated, e.g. by replacing the original shaping elements.
It is an object of the present invention to provide a clinching die free of the drawbacks mentioned above.
It is a further object of the invention to provide a clinching die without a trade-off between strength and yieldability.
It is a further object of the invention to provide such a die without elastomeric elements.
It is a further object of the invention to provide a clinching die which is destroyed upon manipulation.
A further object of the invention is a tool set including a die of the invention.
A further object of the invention is such a tool set specially adapted to complementary sockets mounted on a press.